Lewis & Short

per-fămĭlĭāris, e, adj.,

  1. I. very intimate, very familiar (class.): perfamiliaris Philisto, Cic. Q. Fr. 2, 11 (13), 4.
    In tmesi: Phaedon Socrati per fuit familiaris, Gell. 2, 18, 1.
  2. II. Subst.: perfămĭlĭāris, is, m., a very intimate or familiar friend (class.): meus, Cic. Fam. 13, 51: Epicuri, id. Fin. 5, 31, 94: M. Antonii, id. Brut. 45, 168.